Class JEE Mathematics ALL Q #1202
KNOWLEDGE BASED
APPLY
4 Marks 2026 JEE Main 2026 (Online) 22 January Morning Shift NUMERICAL
Let $A=\begin{bmatrix}2&3\\3&5\end{bmatrix}$ , then $|A^{2025}-3A^{2024}-A^{2023}|$ is equal to .

AI Tutor Explanation

Powered by Gemini

Step-by-Step Solution

Step 1: Factor out $A^{2023}$ We can factor out $A^{2023}$ from the expression inside the determinant: $|A^{2025} - 3A^{2024} - A^{2023}| = |A^{2023}(A^2 - 3A - I)|$
Step 2: Use determinant properties Using the property $|AB| = |A||B|$, we have: $|A^{2023}(A^2 - 3A - I)| = |A^{2023}| |A^2 - 3A - I| = |A|^{2023} |A^2 - 3A - I|$
Step 3: Calculate $|A|$ $|A| = (2)(5) - (3)(3) = 10 - 9 = 1$
Step 4: Calculate $A^2$ $A^2 = \begin{bmatrix}2&3\\3&5\end{bmatrix} \begin{bmatrix}2&3\\3&5\end{bmatrix} = \begin{bmatrix}4+9&6+15\\6+15&9+25\end{bmatrix} = \begin{bmatrix}13&21\\21&34\end{bmatrix}$
Step 5: Calculate $A^2 - 3A - I$ $A^2 - 3A - I = \begin{bmatrix}13&21\\21&34\end{bmatrix} - 3\begin{bmatrix}2&3\\3&5\end{bmatrix} - \begin{bmatrix}1&0\\0&1\end{bmatrix} = \begin{bmatrix}13&21\\21&34\end{bmatrix} - \begin{bmatrix}6&9\\9&15\end{bmatrix} - \begin{bmatrix}1&0\\0&1\end{bmatrix} = \begin{bmatrix}13-6-1&21-9-0\\21-9-0&34-15-1\end{bmatrix} = \begin{bmatrix}6&12\\12&18\end{bmatrix}$
Step 6: Calculate $|A^2 - 3A - I|$ $|A^2 - 3A - I| = (6)(18) - (12)(12) = 108 - 144 = -36$
Step 7: Calculate $|A|^{2023} |A^2 - 3A - I|$ $|A|^{2023} |A^2 - 3A - I| = (1)^{2023} (-36) = 1 \cdot (-36) = -36$
Step 8: Take the absolute value Since the question asks for the absolute value, we have: $|-36| = 36$

Correct Answer: 36

Pedagogical Audit
Bloom's Analysis: This is an APPLY question because it requires the student to apply the properties of determinants and matrix operations to solve the problem. The student needs to know how to calculate the determinant of a matrix, how to perform matrix multiplication and subtraction, and how to use the property $|AB| = |A||B|$.
Knowledge Dimension: PROCEDURAL
Justification: The question requires the student to follow a specific procedure to solve the problem, including calculating the determinant of a matrix, performing matrix multiplication and subtraction, and using the property $|AB| = |A||B|$. The student must know the correct order of operations and how to apply the relevant formulas.
Syllabus Audit: In the context of JEE, this is classified as KNOWLEDGE. The question directly tests the student's knowledge of matrix operations and determinant properties, which are standard topics covered in the JEE syllabus.

AI generated content. Review strictly for academic accuracy.